Rectifier device



Filed Mrch 8, 1959 Patented Dec. 3l, '1940 PATENT RECTIFIER DEVICE Gtmar Geisler, Nuremberg, Germany, assigner to Suddeutsche Apparate-Fabrik G. m. b. H., Nuremberg, Germany, a company Application March 8, 1939, Serial No. 260,515

VIl Claims. (Cl. 175-366) This application is a continuation in part of my copending U. S. application Ser. No. 65,577, filed February 25, 1936. l

The use of selenium rectiers for the purpose 5 of rectifying alternating current is well known in the art. This type of rectiiers or rectifier valves generally consists of a base plate of a ferrous metal and a layer of selenium intimately united with the surface of said iron plate. Durl ing the manufacturing process of such rectlers. the layer of selenium when applied to the base plate is converted into its grey-crystalline state by means of a heat treatment, whereupon the crystalline surface is coated, preferably by sput- 15 tering, with any suitable metal or metal alloy which acts as the counter-electrode of the rectifier valve.

It is well known that the load capacity of a selenium rectifier depends upon the ratio of the 20 traversing current to the return current. In fact,

the lower the resistance becomes in the traversing direction and the higher the resistance oiered in the return or choking direction, the superior is the capacity of the rectiner. In order to im- 25 prove this ratio it has been proposed to add small quantities of earth metals, preferably cerium, to the selenium layer above referred to. It was possible on account of this expedient to considerably increase the eniciency of selenium rectifier 30 valves. y

Careful investigations carried out in this field Vby applicant have proven that it is possible to still involve a considerable improvement with respect to the properties of selenium rectiiiers 35 when small quantities of any halogen compound are added to the selenium layer. The results thus obtained according to the above given rule are superior over those obtained in accordance with the heretofore known method of adding 40 earth metal or earth metal compounds to the selenium layer.

My invention will be more readily understood from the following description taken in conjunction with the accompanying drawing, the single 45 figure of which shows a side view of a selenium rectifier of any conventional type to which the teachings according to my present invention may be applied.

This rectifier consists of two plates or elec- 50 trodes A and B with an intermediate layer C of selenium. The lead -D connects the electrode plate B of the rectier with one terminal of an alternatingcurrent generator (not shown), the other terminal of which is directly connected E through conductor F with the minus pole of a continuous current load likewise not shown since this load is immaterial in connection with this invention. The plus pole of this load is connected with the electrode plate A of the rectifier A, B, C by means of the lead E.

According to the main feature of this invention the property of the selenium layer of rectifiers of the above mentioned type is essentially improved when small quantities, that is a low percentage by weight of any halogen compound of earth metals, alkaline earth metals and rare earths, are added to the selenium layer of the rectiiier. It has been found that the resistance offered in the traversing current direction of the selenium layer relative to a constant resistance in the blocking or choking direction is considerably reduced when any or several of the above identied compounds are added to the selenium layer. Rectifier valves manufactured in accordance with the rule stated above may consequently be operated with considerably higher powers than the heretofore known types of rectliiers without subjecting the electrode plates to a temperature augment, since the Joulean losses are substantially reduced in rectiiier devices produced in accordance with this invention.

Superior improvements in the above mentioned sense are obtained with halogens when either of the iodide compounds cerium iodide, thorium 80 iodide or zirconium iodide is added in small quantities to the selenium layer of the rectifier.

Also bromide, chloride and fluoride compounds of cerium, thorium and zirconium such as cerium bromide,4 thorium bromide, zirconium bromide, cerium chloride, thorium chloride, zirconium chloride, cerium fluoride, thorium fluoride, zirconium iiuoride and the like added in small quantities to .the layer of selenium beneficially improve the efliciency of the rectier. Among the above mentioned compounds, the cerium bromide has beenl found to involve the most satisfactory results.

Even halogenous compounds of alkaline earth metals and rare earths when added in .small amounts to the selenium layer of a rectiner valve satisfactorily improve the properties thereof.

The halogen compounds involve the essential advantage that they are readily soluble in selenium so that it is possible to ensure a perfect and uniform distribution of these compounds in and on the layer of selenium.

The above mentioned halogen compounds may be added as a'. solvent to the selenium before its application to the base plate in which case an extremely tine distribution of the compound in the selenium layer is obtained. However, itis likewise possible to add the compound in the form of a powder to the likewisepulverized selenium 'during the course ot preparation and to remelt the resulting mixture, or the compound may be added in any suitable state to the 'selenium in its molten condition.

The benemzial effect according to the invention is also obtained in cases that. in laddition to small quantities oi' halogen compounds. other known compounds are added to the selenium layer. It is also possible to improve the properties of selenium rectiners by adding to the selenium layer any compound, either metallic constituent of which forms a new compound with the selenium without departing from the scope of this invention. a

What is claimed is:

vadded a metal halideiconsistinz of a haloeen and w cerium.

4. A rectiiier device comprising two electrode plates and an intermediate layer therebetween le essentially consisting ot selenium to which .is added the metal halide eerium chloride.

OTMAR GEIIISLEZR..` 

